This project was initiated to study the role of the catecholamines in the central and peripheral nervous system in experimental hypertension. There is an elevation of the adrenaline-forming enzyme (PMNT) in young (14-week-old) spontaneous hypertensive rats but not in adult animals in which hypertension is fully developed. A decreased amount of noradrenaline and dopamine Beta hydroxylase in selective areas of the anterior and posterior hypothalamus in spontaneous hypertensive and DOCA salt animals was found. BIBLIOGRAPHIC REFERENCES: Kebabian, J.S., Saavedra, J.M., and Axelrod, J.: A Sensitive Enzymatic-Radioisotopic Assay for 3,4-Dihydroxyphenylacetic Acid. J. Neurochem. 28: 795-801, 1977. Saavedra, J.M., Grobecker, H., and Axelrod, J.: Biochemical and Morphologic Study of Catecholamine Metabolism in Spontaneously Hypertensive Rats. Mayo Clin. Proc. 52: 391-394, 1977.